Synaptic transmission underlies essentially all central and peripheral nervous system function. The most critical synaptic processes occur within the first few milliseconds after action potential activation and entail multiple correlated events involving structures of sub-micron dimensions. An imaging system for study of synaptic function must, therefore, be capable of multicolor operation with both high spatial resolution and sub-millisecond time resolution. Unfortunately, there are very few imaging systems available that have all these characteristics. This application describes development of a microscopic detection system for neuroscience research that can image two-colors simultaneously or in fast sequence with both sub-millisecond time resolution and sub-micron spatial resolution. The project has two aims: (1) to build an optical device that will place the images of two different fluorescent probes side-by-side on a conventional COD chip and integrate this module with an acousto-optic tunable filter based illumination system; (2) to demonstrate the potential of this system by simultaneously imaging the spatial distribution of pre- and post-synaptic calcium entry into the adult frog neuromuscular junction in the first few milliseconds after stimulation. This work is designed to lead to a more ambitious Phase II project extending to millisecond imaging of more than two colors.